Integrated photonics offers significant advantages over fiber and free-space optics for a wide range of applications due to its ability to miniaturize optical fields while maintaining high degrees of robustness, resulting in reduced size, weight, and power consumption. Currently, one of the most significant limiting factors facing integrated photonics is the difficulty in interfacing with fiber optics. In coupling light from a fiber to a waveguide, several decibels of power are typically lost.
In prior approaches, lensed fibers or ultra-high numerical aperture fibers are butt-coupled to inverse tapers in integrated photonics chips. The minimum total facet loss that has been achieved in this way is about 0.4 dB, which corresponds to roughly 90% coupling efficiency. However, for many applications an even higher efficiency, ideally approaching 100%, is desired.
Thus, there is a need for a high-efficiency coupler with the flexibility to be applied to many different integrated photonics platforms.